Fluorescent lamp



Feb. 2, 1943. i G. T. SCHMIDLING 2,309,675

FLUORESCENT LAMP Filed DBG. 12, 1959 INVENTOR ATTORN E Patented Feb. 2, 1943 'UNITED STATES PATENT OFFICE FLUORESCENT LAMP Gilbert T.l Schmdling, New York, N. Y., asslgnor of one-half to Charles Melzak, Yonkers, N. Y.

Application December 12, 1939, Serial No. 308,795

Claims.

The present invention relates to lighting fixtures and more particularly to lighting fixture of the type utilizing fluorescent tubes.

Among the problems associated with the present types of lamps utilizing fluorescent tubes is that the tubes turn black after a few hundred hours of use. This is due in part to the condensation of excess mercury vapor for a given operating current and temperature and in part to the evaporation of metals and metallic salts from the hot cathode. The present invention aims to minimize or overcome the above dilculty.

Another problem in fluorescent lighting is to obtain the proper color quality of light. Usually sunlight is the most desirable quality, but, heretofore, attempts to reproduce it with fluorescent lamps have been unsuccessful.

A feature of the invention is the provision of a coating for the lighting tubes which will give light with optimum color quality equivalent to the average skyshine plus noon sunlight.

A third feature of the invention is the provision of a unitary lighting fixture which can be readily substituted for the present types of lighting fixtures utilizing incandescent lamps and which can be connected to the usual 110 volt lighting circuit. The fixture is designed to give maximum lighting effect and comfort at a minimum cost.

An object of the present invention is to minimize or prevent darkening of fluorescent lighting tubes and thereby increase their life and efciency,

Another object of the present invention is to localize the condensation of excess mercury vapor in a proportion of the tube where it will not impair the lighting efficiency of the tube.

Another object of the invention is to localize the condensatiorli'of excess mercury vapor in offset protuberances adjacent the electrodes of the tube to make the protuberances more effective.

Another object of the invention is to provide an improved iiuorescent material for coating fluorescent tubes.

Another object of the invention is to provide an improved uorescent material which will produce light of a color quality equivalent to or approximating skyshine plus noon sunlight.

A further object of the invention is to provide a unitary lighting fixture employing a fluorescent tube which may be readily substituted for fixtures now in use employing the less eicient and less desirable incandescent lamps.

A still further object of the invention is to provide an improved unitary lighting fixture utilizing a fluorescent tube which may be connected to the ordinary volt lighting circuit.

Other and further objects ofthe invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawing, forming a part of the specification,

wherein Fig. 1 is a vertical cross-sectional view of an embodiment of the fixture with parts shown in elevation;

Fig. 2 is a bottom view of the fixture;

Fig. 3 is a detailed sectional view along the line 3-3 of Fig. 2, illustrating the location of the electrode and its attachment at the end of the tube and also the offset protuberance; Fig. 4 is a horizontal section along the line 4-4 of Fig. 3 through the end of the tube showing the protuberance and the fluorescent coating; Fig. 5 is a sectional view along the line 5--5 of Fig. 4 showing the fluorescent coating;

Fig. 6 is a sectional view of the preferred embodiment of the invention; and

Fig. 7 is a sectional view of another embodi- V ment of the invention.

Referring again to the drawing and more particularly to Fig. 1 thereof, there is shown a lighting xture having a supporting tube l of the gen eral type commonly used as a support and electrical conduit for ceiling lights utilizing incandescent lamps. A bell shaped housing 2 may be threaded at its upper end to the supporting tube l and a reflector may be secured to the lower periphery of the housing in any suitable manner. As illustrated in the drawing the peripheryof the housing is interlocked with the periphery of the reflector as shown at 5. Preferably the housing is spaced sufficiently far from the upper side of the reflector to provide space for a transformer E, which increases the voltage of the usual 110 lighting circuit suicient to give optimum operating conditions for a fluorescent tube of the type used in the fixture. The transformer may be mounted on a support or basket l bridging the raised portions 8 of the reflector. The reflector 4 may have any desired shape to create the proper distribution of light.. As shown in Fig. 1 the raised portion 8 provides a circular groove or trough on the bright side of the reector for receiving the circular fluorescent tube 9. The central portion may be domed downwardly as shown at I and the zone intermediate the portion 8 and the periphery may be curved downwardly to give a proper distribution and concentration of iight from the lighting tube 9. The circular tube is particularly adapted for a single suspension and affords a more uniform distribution of light than one or more straight tubes. The length of the tube may be much greater than a straight tube with a given size of fixture.

While various types of tubes may be used in the fixture, the preferred embodiment of fluorescent tube has distinct advantages. Preferably the ends of the tube extend upwardly as shown at I2 in Figs. 1 and 3. The electrode I4 extends downwardly into the upwardly extending end I2 of the fluorescent tube 9 and preferably terminates above the end of the circular portion of the tube. As a protection against darkening of the circular portion of the fluorescent tube by condensation, a protuberance I5 is provided at each end of the circular tube and at or adjacent the ends of the electrodes. The protuberances I5 are rendered more effective by enveloping the outer surface of the protuberance with a heat conducting or heat absorbing material as shown at I6. Since the tendency of the mercury vapor to condense is greatest at the coolest part of the tube, the condensation of excess mercury vapor will be conned to the protuberances which are not in the path of discharge and thus darkening of the tube will be prevented. Preferably also metal supporting members are attached yto the protuberances to serve the two-fold function of supporting the fluorescent tube at said portions and to conduct away the heat to keep the protuberances colder than the other portions of the tube. Thus the condensation of the mercury vapor is concentrated in and substantially confined to the protuberances I5 which are located at the point where the tendency to condensate is greatest and are maintained at a lower temperature than the rest of the tube. By means of the metal coated protuberances and the location of the electrodes in the upwardly extending ends I2 condensation in the circular or fluorescent portion of the tube 9 is minimized or prevented, together with the resulting darkening of the tube caused thereby. Thus the original eflciency 0f the tube is maintained and the useful life of the tube is greatly prolonged. The eiciency of the tube is further increased by forming the electrode of substantially pure Swedish iron without coatings of any kind. This minimizes the evaporation of metals and metallic salts from the cathode.

The circular fluorescent tube may be mounted on the reflector by means of the supporting members I'I. engaging the protuberances I5 and by means of another supporting member I8. Preferably the upwardly extending ends I 2 of the tube project into the sockets 21 mounted in apertures I9 in the reflector. The conductors leading from the cathode detachably connect the metallic disc 28 on the upwardly extending end I2 of the tube. A spring 29 operatively connected with secondary of the transformer by the conductor 20 presses against the metal ring 28. Thus the metal brackets I1 and I8 hold the tube against the spring 29 to maintain it in electrical contact with the source of current. In this way the uorescent tubes may be removed and replaced with the ease of incandescent lamps. The primary of the transformer is connected with the conductors passing through the suspending tube I and connected with the usual volt alternating current supply. The units may be readily substituted for the ceiling lights in factories and other buildings which now use ceiling suspended fixtures for incandescent lamps. This can be done without changes in the wiring of the building or in the present voltages supplied to the building.

A further important feature of the invention is the fluorescent material used in coating the tubes 9. The known types of fluorescent lamps have too much blue light for use as domestic or industrial illumination. Attemps have been made to simulate daylight and optimum color quality but without success.

A fluorescent material is used herein which when excited by the twenty-five thirty-seven Angstrom unit line from mercury vapor gives a fluorescent color, which in combination with the visible light from the mercury vapor when the tube is operating at 240 milli-amperes, in a tube one inch in diameter, gives a specific quality oi' daylight which is equivalent to a combination of sunlight and standard daylight; that is, the color quality is such that it is the equivalent of average skyshine plus noon sunlight. The exact duplication of color in these lamps is obtained by a color equalizer which makes use of a uorescent material containing in its spectrum a portion of two of the other colors. Preferably, three colors are used.

A great deal of waste results when only two colors are used in making fluorescent combinations because of the variations in color which normally occur in the manufacture of uorescent materials and which cannot be overcome due to manufacturing limitations. Instead of relying on two colors only, the present invention uses manganese activated zinc ortho-silicate to produce a green balancing color. I have found that much better control can be obtained in this way which results in uniform quality of light being emitted from all tubes. Another advantage in using the green producing material as a balancer is due to the fact that it is a more efficient producer of blue than the calcium tungstate ordinarily used, and therefore not so much of the relatively inefcient calcium tungstate is required.

The preferred embodiment of fluorescent material used herein may be made from the following compounds in the proportions indicated:

Grams Beryllium zinc ortho-silicate 75 Zinc ortho-silicate 16.7 Calcium tungstate 48.7

The beryllium and zinc in the beryllium zinc ortho-silicate are in molecular proportions, and an activator of about 2.5% of manganese is utilized. This makes a fluorescent material, which is very rich in red radiation. The zinc orthosilicate is activated by about .8% manganese and the calcium tungstate is activated by about .2% lead.

The fluorescent material is coated on the inside wall of the glass tube, by using well-known methods. The lamp is exhausted, after which a. drop of mercury is placed in the tube and the tube is then filled with a rare gas, such as argon, or mixtures of rare gases. A metallic electrode, such as pure iron, has been found to give best results without coatings of any kind. Such an electrode minimizes deposits on the fluorescent surface, thereby maintaining the efclency of the lamp over long periods of use. Lamps and fluorescent tubes made in this way, retained 96% oftheir initial luminous efiiciency after 2000 hours of continuous burning.

It wil1 be understood that various shapes and types of reflectors may be utilized and one or more tubes may be included in the units. For illustrative purposes a unit is shown in Fig. 6 with a reflector 24 designed to give a dierent distribution of light and a less expensive fixture. The transformer 6a may be mounted in the central depression therein and a piece of metal 26 may extend over and conceal it and to a threaded bushing for attachment extend from a ceiling. In Fig. 7 a unit is shown with a trans-- former 6b and a reflector with three fluorescent tubes 9b mounted thereon to illustrate the use of any desired number of tubes in a fixture.

It will be seen that the present invention provides a unitary lighting fixture utilizing a fluorescent tube which may be connected to standard 110 volt lighting circuits. The unit may be readily substituted for incandescent lamp xtures without changing the wiring or the current supply. lIhus a more efficient and a more desirable color quality light can be installed at a minimum cost in existing factories and buildings. The fluorescent material produces a color quality approximating sunlight more nearly than previous materials used. The construction of the tube localizes the condensation of the mercury vapor and protects the fluorescent coating from being darkened, thereby preserving the efficiency of the tube and greatly prolonging its useful life. The units are simple in construction, inexpensive to manufacture, land suiiiciently rugged to withstand the rough usage to whichthey may be subjected.

As various changes may be made in the form, construction and arrangement of the parts herein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim:

1. In a fluorescent lighting device, the combination of a fluorescent tube for a lighting fixture having an offset protuberance adjacent one end thereof, fluorescent oxide material adhered to the inside of the tube, and heat absorbing means in engagement with said protuberance to minimize discoloration of the coating on the inside of the tube.

2. In a fluorescent lighting device, the combination of a iluorescent tube for a lighting fixture having offset protuberances adjacent the ends thereof, fluorescent oxide materials adhered to the inside of the tube and heat absorbing means in engagement with said protuberances to prevent discoloration of the coating on the inside of the tube.

3. In a fluorescent lighting device, the combination of a fluorescent tube for a lighting fixture having electrodes therein for supplying current thereto, fluorescent oxide material in the tube and an offset protuberance adjacent one of said electrodes for collecting the condensed metallic particles in the tube and to minimize darkening of the tube except in said protuberance.

4. In a fluorescent lighting device, the combination of a fluorescent tube for a lighting xture having electrodes therein for supplying current thereto, and an offset protuberance adjacent each of said electrodes for collecting the condensed mercury oxides in the tube and to minimize darkening of the tube except in said protuberances.

5. In a fluorescent lighting device, the combination of a fluorescent tube for a lighting fixture having electrodes therein for supplying current thereto, and having a fluorescent material adhered to the inner walls thereof, an oiset protuberance adjacent one of said electrodes for collecting the metallic condensationproducts in the tube and to minimize darkening of the tube except in said protuberance, and means for reducing the temperature of said protuberance to localize the darkening of the tube by the metallic condensation products.

6. In a fluorescent lighting device, the combination of a fluorescent tube for a lighting fixture having electrodes therein, fluorescent material in the tube, adapted in use to liberate oxygen and means for reducing the temperature of the tube at a predetermined portion thereof to localize the condensation of mercury oxides and to minimize the darkening of the rest of the tube as a result oi' continued use thereof.

7. In a fluorescent lighting device, the combination of a fluorescent tube for a lighting xture having a fiuorescentoxide material adhered r to the inside thereof, said tube having mercury vapor as one of its constituents and having an offset protuberance therein and heat absorbing means in engagement with said protuberance to reduce the temperature thereof and to localize the condensation of the mercury oxides, thereby to minimize darkening of the rest of the tube.

8. In a fluorescent lighting device, the combination of a uorescent tube for a lighting xture having mercury vapor as one of its constituents and having offset protuberances therein, a fluorescent material therein having by weight seventy parts of beryllium zinc ortho-silicate, seventeen parts of zinc ortho-silicate, and fifty parts of calcium tungstate, supporting means for said tube attached to said protuberances, said supporting means being heat conducting or heat absorbing to reduce the temperature of said protuberances and to localize the condensation of the metallic particles, thereby to minimize the darkening of the rest of the tubes.

9. In a fluorescent lighting device, the combination of a fluorescent tube having fluorescent material adhered to the inside thereof and having mercury vapor as an element therein, spaced tubular portions extending at an angle to said fluorescent tube, electrodes mounted in said spaced tubular portions, offset protuberances adjacent said spaced tubular portions and means for reducing the temperature of said protuberance to localize the condensation of mercury vapor in the tube and minimize the darkening of the other portions of the tube.

l0. A fluorescent material for coating lighting tubes comprising seventy-five parts by weight of beryllium zinc ortho-silicate activated yby about 2.5% of manganese. seventeen parts of zinc orthovated by about .2% of lead.

GEBERT T. SCHMIDLING. 

